Placenta's oxygen tanks for early embryos revealed

Placenta's oxygen tanks for early embryos revealed

It had been believed that the yolk sac contributed the bulk of oxygen at this stage but recent studies have shown that this gradually decreases in importance as the embryo ages. The heart begins beating at around four weeks but oxygen is still supplied by the mother.

The new research reveals how the early placenta solves the problem of supplying oxygen to the growing embryo in the second and third months of pregnancy, as it gradually takes over this role from the yolk sac.
 
The scientists show that as the placenta grows in the first few weeks, small groups of stem cells are formed from which primitive red blood cells arise. These cells are able to gather up and store oxygen under the unusually low concentrations found at the implantation site.
 
Blood vessels gradually grow towards these cell groups, leading to the slow release of oxygen-laden red cells to the embryo and keeping it supplied until more efficient oxygen transfer becomes possible as maternal blood enters the placenta at the end of the third month.

http://www.manchester.ac.uk/discover/news/article/?id=15107
Edited

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